Re: arrays of objects.

[Juan Pablo Carbajal]

On Tue, Feb 5, 2013 at 10:21 AM, Juan Pablo Carbajal
<address@hidden> wrote:
> On Tue, Feb 5, 2013 at 12:02 AM, ernst <address@hidden> wrote:
>> Hi Juan,
>>
>> if you don't mind that the example I give you is not useful,
>> i can give you a quite simple one:
>>
>> constructor:
>>
>> function num = pn(dNum)
>>
>>   switch (nargin)
>>     case 0
>>       dNum = 0.0;
>>     case 1
>>       % nothing to do
>>     otherwise
>>       print_usage();
>>   endswitch
>>
>>   if ~isa(dNum, 'double')
>>      error(strcat('invalid type: ',class(dNum)));
>>    endif
>>   num.dNum = dNum;
>>   num = class(num, 'pn');
>> endfunction
>>
>> As you can see, i just wrap a double in a class object.
>>
>> The converse, is also easy:
>>
>> function dNum = doubleValue(num)
>>    dNum = num.dNum;
>> endfunction
>>
>>
>> With this setting, you can reproduce what I wrote before (see below),
>> right?
>>
>> greetings, Ernst
>>
>>
>>> On Mon, Feb 4, 2013 at 10:25 PM, ernst <address@hidden> wrote:
>>>> Hi all,
>>>> I want to make octave use another kind of number
>>>> (just think of intervals, rationals, continued fractions.....) almost
>>>> like using the builtin types.
>>>> To this end, i have a class pn and constructor invocation like pn(3.4).
>>>>
>>>> This already works quite well, I can do some basic programming works in
>>>> octave
>>>> using my own numbers.
>>>> I can even use vectors and matrices: [pn(2) pn3); pn(4) pn(5)] works.
>>>>
>>>> BUT: I have problems with higher dimensional objects.
>>>> One example is arrayfun:
>>>> On the one hand side,  a=arrayfun(@pn,rand(2,3,4)) seem to work,
>>>> on the other hand, arrayfun(@doubleValue,a) does not work,
>>>> raising
>>>>
>>>> "error: can't perform indexing operations for class type",
>>>>
>>>> although doubleValue(pn(3)) does the correct conversion to double as
>>>> expected.
>>>>
>>>> I tried with arrayfun with doubles and with chars, both work well.
>>>> Does it make sense, not to allow general classes?
>>>> How does Matlab react?? (i dont have one, because it is too expensive).
>>>>
>>>> The alternative would be, to provide array-indexing for my class, but i
>>>> think, this makes no sense,
>>>> because i just want to use the indexing provided by octave.
>>>> I have the idea it must be like for java or c, where array indexing
>>>> is not needed to be implemented for each type.
>>>>
>>>> Help very much apprechiated.
>>>>
>>>> greetings,
>>>>
>>>> Ernst
>>>> _______________________________________________
>>>> Help-octave mailing list
>>>> address@hidden
>>>> https://mailman.cae.wisc.edu/listinfo/help-octave
>>> Can't tell what is the issue without more information, but based on my
>>> own experinece with cellfun, the old class style is not woring very
>>> well inside those functions. Is as if one would need to declare these
>>> functions "friend functions" as in C++.
>>>
>>> Though I can be completely off, not knowing exactly what is your
>>> issue. Maybe you can upload your code to Agora?
>>>
>>
>
> Hi ernst,
>
> People around here like that answers are posted below the previous
> message and not on top.
>
> The problem you hit on is not the one I was referring to. As I
> understand it, in your case, you should get an "invalid argument"
> error rather than the one you get (more cryptic). Why? Since array fun
> expects an array of type (from the help) logic, numeric, string,
> structure or cell and you are passing an array of classes. For
> example, this also would not work
>  arrayfun(@length,[pn(1); pn(2)])
> or any other execution of arrayfun with an array of classes.
>
> It is ok that arrayfun is not working in your case, cause the use you
> want is not implemented. Still there is the problem of the cryptic
> error message.
>
> If you have the time you could report the "Crpytic error message" when
> passing an array of classes to arrayfun in the bug tracker, so this
> issue is not lost. It is very basic to fix, so I will do it asap.
>
> Cheers

Also Ernst,

When you are asking a new question, do not reply to people in another
thread. Just create a new thread by composing a completely new
message. Otherwise two potentially unrelated discussions are merged as
one in the nabble interface.

Cheers